To study the EcoB restriction DNase/ATPase and modification methylase to (1) understand how it can be broken nonspecifically, yet receive only a defined number of breaks; (2) understand the role of each subunit of the enzyme in the reaction; (3) determine the structure of the 3' - and 5' - terminal formed by the DNase, and of the recognition site of the enzymes; (4) understand the significance of the EcoB restriction ATPase; (5) understand the relationship to and interactions with other host and virus metabolic functions; (6) understand the mechanism by which the enzyme "travels" along DNA. To study the reaction of the recBC DNase/ATPase by electron microscopy to learn about its role in DNA recombination. To study the ATPase-mediated melting reaction biochemically. To study the specificity and significance of E. Coli endonucleases III and V and their interaction with the Phage T4 UV endonuclease.